This video describes the fourth major step in the conceptual modeling workflow using Visual MODFLOW Flex: Defining the Model Structure.
Defining the model structure is accomplished using surface data objects to define the model horizons, which frequently delineate the location of model layers. Horizons are stratigraphic layers that define the upper and lower boundaries of the structural zones in a conceptual model. Once these structural zones are created you will use them as the basis for defining property zones during the next workflow step. Each horizon can be assigned a particular type, which defines the relationship to other horizons in the conceptual model. This prevents intersecting layers and establishes layers that satisfy both FEFLOW and MODFLOW requirements. Horizon types include erosional, base, conformable and discontinuity horizons.
Rules associated with each horizon type are listed in the Visual MODFLOW Flex user manual, see the link below: Horizon Rules (link to user manual, see chapter 7.4): https://www.waterloohydrogeologic.com/help/vmod-flex/